Pandas - Search for keyword

Question

I'm trying to search for a keyword in a dataframe and print the keyyword if found using the following code:

if df[df['description'].str.contains(keyword,case=False)]:
    print(keyword)
else:
    print("NOT FOUND")

I'm getting the following error message:

ValueError: The truth value of a DataFrame is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

Any suggestions on how to fix this?

@BigBen that message is incomprehensible for beginners, usually. — user17242583
– user17242583, Commented Dec 9, 2021 at 21:23
Also, I think this might actually be a use for .any(). Usually it's better for the OP to change there code, but here... — user17242583
– user17242583, Commented Dec 9, 2021 at 21:26
@ZLi it can feel like that if you spend most of your SO time in the python tag...:) — user17242583
– user17242583, Commented Dec 9, 2021 at 21:42
@user17242583 I mean I feel there used to be good questions which requires some thinking and more than 1 line as an answer... — Z Li
– Z Li, Commented Dec 9, 2021 at 21:43

user17242583 · Accepted Answer · 2021-12-09 21:29:05Z

2

Try this instead:

if df['description'].str.contains(keyword,case=False).any():
    print(keyword)
else:
    print("NOT FOUND")

df['description'].str.contains(keyword,case=False) returns a column, the same length as df['description'], containing True or False values, where each corresponds to the value of the same index in df['description']. If that value contained the keyword, the value in the returned Series is True, otherwise, False.

Calling .any() on a Series object will return True if at least one value in the Series is True. If all of them are False, .any() will return False.

answered Dec 9, 2021 at 21:29

user17242583

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Comments

David Waterworth · Accepted Answer · 2021-12-09 21:28:17Z

0

Your expression

df[df['description'].str.contains(keyword,case=False)]

Doesn't return a bool, it returns a subset of the original dataframe containing the rows that match the predicate (contains keyword). So as the error message implies you need to test if this dataframe is empty or not.

answered Dec 9, 2021 at 21:28

David Waterworth

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